A cooling system coupled to an engine utilizes an engine-driven pump to circulate coolant for cooling components of the engine in addition to providing heat to a passenger compartment of a vehicle. In hybrid-electric vehicles, an electric auxiliary pump may be included in the system in order to continue heating the passenger compartment during occasions when the engine is off; however, the auxiliary pump is not operated while the engine is running.
One example in which an auxiliary pump is used with an engine-driven pump while the engine is running is disclosed in US Patent Application Publication 2008/0251303. In the cited reference, a high temperature cooling circuit includes an engine-driven water pump and a low temperature cooling circuit includes an electric water pump. Under selected operating conditions, the high temperature and low temperature circuits may be in fluidic communication; however, only one of the two water pumps may be operational. One example in which the water pumps are both operational while the cooling circuits are in fluidic communication is during a cold start of the engine. Once the temperature of the engine rises, however, both pumps remain operational but the cooling circuits operate without fluidic communication between them in order to maintain the lower temperature of the low temperature cooling circuit. As such, the engine-driven pump maintains a high output and does not receive assistance from the electric pump, and still must be sized sufficiently to pump enough flow to manage engine temperatures under continuous heavy engine loads.
The inventors herein have recognized the above issues and have devised an approach to at least partially address them. In one example, a method for a cooling system coupled to an engine in a vehicle is disclosed. The method comprises, during engine off, operating an auxiliary pump to flow coolant through a heater core, and, during engine running, operating an engine pump to flow coolant through the heater core and radiator, and selectively operating the auxiliary pump to assist the flow through the heater core based on operating conditions.
For example, under conditions in which the engine is running and the engine temperature is greater than a threshold temperature, the auxiliary pump may be activated in order to assist the operation of the engine-driven pump in managing engine temperature. In this manner, the power required to operate the engine-driven pump may be maintained at a lower value when less cooling is needed. Furthermore, the engine-driven pump may be downsized due to its lowered output when the auxiliary pump is used while the engine is running and the engine temperature is high.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.